Toxicology Screening in Sports-Related Sudden Cardiac Death: A Multinational Observational Study

BACKGROUND

Knowledge of toxicological findings among sports-related sudden cardiac death (SrSCD) is scarce.

OBJECTIVES

This study aimed to describe postmortem toxicology findings in a multinational cohort of young SrSCD.

METHODS

Patients with sudden cardiac death (SCD) aged 12 to 49 years with a complete post mortem were included from Denmark, Spain, and Australia. Postmortem findings were compared between SrSCD and non-SrSCD, and toxicology findings in SrSCD were assessed.

RESULTS

We included 3,189 SCD, of which 219 (7%) were sports-related. SrSCD patients were younger (36 years vs 41 years; P < 0.001) and of male predominance (96% vs 75%; P < 0.001), and their death was more often caused by structural cardiac disease (68% vs 61%; P = 0.038). Positive toxicology screenings were significantly less likely among SrSCD than non-SrSCD (12% vs 43%; P < 0.001), corresponding to 82% lower odds of a positive toxicology screening in SrSCD. Patient characteristics were similar between SrSCDs with positive and negative toxicology screenings, but deaths were more often unexplained (59% vs 34%). Nonopioid analgesics were the most common finding (3%), and SCD-associated drugs were detected in 6% of SrSCD. SUD was more prevalent among the SrSCD with positive toxicology (59% vs 34%).

CONCLUSIONS

Sports-related SCD mainly occurred in younger men with structural heart disease. They had a significantly lower prevalence of a positive toxicology screening compared with non-SrSCD, and detection of SCD-associated drugs was rare.

Clinical outcomes of 10 years of cardiac screening in elite New Zealand athletes

OBJECTIVES

To report findings from the High Performance Sport New Zealand cardiac screening programme, including comparisons between sexes and ethnicities.

DESIGN

Retrospective cohort study.

METHODS

Elite Olympic-sport athletes were screened (2012-2022) with personal/family history, physical examination, resting 12-lead ECG and followed from the date of first screening until July 2022. An audit reviewed screening records, including demographic data, ECGs, follow-up and diagnoses. Flagged/equivocal ECGs were re-reviewed (International Criteria).

RESULTS

2075 ECGs from 1189 athletes (53 % female, mean age 21 years; 83 % European, 9 % Māori, 5 % Pacific Islander, 3 % other) were included. No athletes retired for cardiac reasons; there were no cardiac deaths or major cardiac incidents (mean follow-up from first screening: 6.1 years (range: 0.6-10.9 years)). Diagnoses included Wolff-Parkinson-White (WPW) syndrome (0.7 %) and cardiomyopathies (0.3 %). Overall, 3.5 % of ECGs were abnormal, with ECGs of females more commonly abnormal (4.4 % vs 2.5 %, p = 0.02) and with a higher proportion of ECGs with abnormal T-wave inversion (TWI) (3.1 % vs 0.9 %, p < 0.001) compared to males. Of the abnormal TWI in females (all aged ≥16 years), 47 % was limited to V1-V3 with no other abnormalities. Abnormality rates were similar between Māori, Pacific Islander and European athlete ECGs.

CONCLUSIONS

WPW was the most frequent diagnosis, with very little cardiomyopathy found. The proportion of abnormal ECGs was low overall, but higher in females. This was driven by anterior TWI in V1-V3 which was not associated with diagnoses of conditions associated with sudden cardiac death (SCD). There was no difference in the proportion of abnormal ECGs of Māori or Pacific Island athletes compared to European athletes.

A case series of patients with filamin-C truncating variants attending a specialized cardiac genetic clinic

Background

FLNC encodes for filamin-C, a protein expressed in Z-discs of cardiac and skeletal muscle, involved in intracellular signalling and mechanical stabilization. Variants can cause diverse phenotypes with skeletal (myofibrillar or distal myopathy) and/or cardiac (hypertrophic, restrictive, and arrhythmogenic cardiomyopathies) manifestations. Truncating variants have recently been implicated in arrhythmogenic cardiomyopathy (ACM) without skeletal disease.

Case summary

Retrospective review of medical records, including cardiac investigations, was performed for families attending a specialized clinic with a FLNC truncating variant (FLNCtv). Variants were classified according to accepted variant interpretation criteria. Of seven families identified, six had primary cardiac phenotypes with one nonsense and five frameshift variants (nonsense-mediated decay competent) identified. One family had no cardiac phenotype, with a pathogenic variant (p.Arg2467Alafs*62) identified as secondary genetic finding. Of the six with cardiac phenotypes, proband age at diagnosis ranged 27-35 years (four females). Five families experienced sudden cardiac death (SCD) of a young relative (age range: 30-43 years), and one patient listed for cardiac transplant. Left ventricular (LV) ejection fraction ranged from 13 to 46%, with LV fibrosis (late gadolinium enhancement) on cardiac imaging or on postmortem histology seen in three families. Two families had one genotype-positive/phenotype-negative relative.

Discussion

The FLNCtv causes a left-sided ACM phenotype with a high risk of severe cardiac outcomes including end-stage heart failure and SCD. Incomplete penetrance is observed with implications for reporting secondary genetic findings.

The burden of splice-disrupting variants in inherited heart disease and unexplained sudden cardiac death

There is an incomplete understanding of the burden of splice-disrupting variants in definitively associated inherited heart disease genes and whether these genes can amplify from blood RNA to support functional confirmation of splicing outcomes. We performed burden testing of rare splice-disrupting variants in people with inherited heart disease and sudden unexplained death compared to 125,748 population controls. ClinGen definitively disease-associated inherited heart disease genes were amplified using RNA extracted from fresh blood, derived cardiomyocytes, and myectomy tissue. Variants were functionally assessed and classified for pathogenicity. We found 88 in silico-predicted splice-disrupting variants in 128 out of 1242 (10.3%) unrelated participants. There was an excess burden of splice-disrupting variants in PKP2 (5.9%), FLNC (2.7%), TTN (2.8%), MYBPC3 (8.2%) and MYH7 (1.3%), in distinct cardiomyopathy subtypes, and KCNQ1 (3.6%) in long QT syndrome. Blood RNA supported the amplification of 21 out of 31 definitive disease-associated inherited heart disease genes. Our functional studies confirmed altered splicing in six variants. Eleven variants of uncertain significance were reclassified as likely pathogenic based on functional studies and six were used for cascade genetic testing in 12 family members. Our study highlights that splice-disrupting variants are a significant cause of inherited heart disease, and that analysis of blood RNA confirms splicing outcomes and supports variant pathogenicity classification.

The role of genetic testing in diagnosis and care of inherited cardiac conditions in a specialised multidisciplinary clinic

BACKGROUND

The diagnostic yield of genetic testing for inherited cardiac diseases is up to 40% and is primarily indicated for screening of at-risk relatives. Here, we evaluate the role of genomics in diagnosis and management among consecutive individuals attending a specialised clinic and identify those with the highest likelihood of having a monogenic disease.

METHODS

A retrospective audit of 1697 consecutive, unrelated probands referred to a specialised, multidisciplinary clinic between 2002 and 2020 was performed. A concordant clinical and genetic diagnosis was considered solved. Cases were classified as likely monogenic based on a score comprising a positive family history, young age at onset, and severe phenotype, whereas low-scoring cases were considered to have a likely complex aetiology. The impact of a genetic diagnosis was evaluated.

RESULTS

A total of 888 probands fulfilled the inclusion criteria, and genetic testing identified likely pathogenic or pathogenic (LP/P) variants in 330 individuals (37%) and suspicious variants of uncertain significance (VUS) in 73 (8%). Research-focused efforts identified 46 (5%) variants, missed by conventional genetic testing. Where a variant was identified, this changed or clarified the final diagnosis in a clinically useful way for 51 (13%). The yield of suspicious VUS across ancestry groups ranged from 15 to 20%, compared to only 10% among Europeans. Even when the clinical diagnosis was uncertain, those with the most monogenic disease features had the greatest diagnostic yield from genetic testing.

CONCLUSIONS

Research-focused efforts can increase the diagnostic yield by up to 5%. Where a variant is identified, this will have clinical utility beyond family screening in 13%. We demonstrate the value of genomics in reaching an overall diagnosis and highlight inequities based on ancestry. Acknowledging our incomplete understanding of disease phenotypes, we propose a framework for prioritising likely monogenic cases to solve their underlying cause of disease.

Concealed Cardiomyopathy in Autopsy-Inconclusive Cases of Sudden Cardiac Death and Implications for Families

BACKGROUND

Genetic testing following sudden cardiac death (SCD) is currently guided by autopsy findings, despite the inherent challenges of autopsy examination and mounting evidence that malignant arrhythmia may occur before structural changes in inherited cardiomyopathy, so-called "concealed cardiomyopathy" (CCM).

OBJECTIVES

The authors sought to identify the spectrum of genes implicated in autopsy-inconclusive SCD and describe the impact of identifying CCM on the ongoing care of SCD families.

METHODS

Using a standardized framework for adjudication, autopsy-inconclusive SCD cases were identified as having a structurally normal heart or subdiagnostic findings of uncertain significance on autopsy. Genetic variants were classified for pathogenicity using the American College of Medical Genetics and Genomics guidelines. Family follow-up was performed where possible.

RESULTS

Twenty disease-causing variants were identified among 91 autopsy-inconclusive SCD cases (mean age 25.4 ± 10.7 years) with a similar rate regardless of the presence or absence of subdiagnostic findings (25.5% vs 18.2%; P = 0.398). Cardiomyopathy-associated genes harbored 70% of clinically actionable variants and were overrepresented in cases with subdiagnostic structural changes at autopsy (79% vs 21%; P = 0.038). Six of the 20 disease-causing variants identified were in genes implicated in arrhythmogenic cardiomyopathy. Nearly two-thirds of genotype-positive relatives had an observable phenotype either at initial assessment or subsequent follow-up, and 27 genotype-negative first-degree relatives were released from ongoing screening.

CONCLUSIONS

Phenotype-directed genetic testing following SCD risks under recognition of CCM. Comprehensive evaluation of the decedent should include assessment of genes implicated in cardiomyopathy in addition to primary arrhythmias to improve diagnosis of CCM and optimize care for families.

“Concealed cardiomyopathy” is an important cause of autopsy-inconclusive sudden cardiac death and diagnosis impacts care of surviving relatives

Background

Genetic testing following sudden cardiac death (SCD) is currently guided by autopsy findings, despite the inherent challenges of autopsy examination and mounting evidence that malignant arrhythmia may occur prior to structural changes in inherited cardiomyopathy, so-called “concealed cardiomyopathy” (CCM).

Purpose

To identify the spectrum of genes implicated in autopsy-inconclusive SCD and describe the importance of identifying CCM for the ongoing care of SCD families.

Methods

Using a standardised framework for adjudication, autopsy-inconclusive SCD cases were identified as having a structurally normal heart or sub-diagnostic findings of uncertain significance on autopsy. Genetic variants were classified for pathogenicity using the American College of Medical Genetics and Genomics guidelines. Family follow-up was performed where possible.

Results

Twenty disease-causing variants were identified among 91 autopsy-inconclusive SCD cases (mean age 25.4±10.7 years) with a similar rate regardless of the presence or absence of sub-diagnostic findings (25.5% vs 18.2%, p=0.40). Cardiomyopathy-associated genes harboured 70% of clinically-actionable variants and were overrepresented in cases with sub-diagnostic structural changes at autopsy, accounting for 11 out of 12 disease-causing variants in this group (79% vs 21%, p=0.038, Figure 1, panel A). Variants in arrhythmogenic cardiomyopathy genes were the most common cause of CCM (9/14 CCM cases, Figure 1, panel B). Nearly two-thirds of genotype-positive relatives had an observable phenotype either on initial assessment or during subsequent follow-up. Twenty-seven genotype-negative first-degree relatives were released from ongoing screening.

Conclusion

The current paradigm of phenotype-directed genetic testing following SCD risks under recognition of CCM. Comprehensive evaluation of the decedent should include assessment of genes implicated in both cardiomyopathy and primary arrhythmias to improve diagnosis of CCM and optimise care for families.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Heart Foundation of Australia and National Health and Medical Research CouncilNew South Wales Health

"Concealed cardiomyopathy" as a cause of previously unexplained sudden cardiac arrest

BACKGROUND

Genetic heart disease is a common cause of sudden cardiac arrest (SCA) in the young and those without an ischaemic precipitant. Identifying a cause of SCA in these patients allows for targeted care and family screening. Current guidelines recommend limited, phenotype-guided genetic testing in SCA survivors where a specific genetic condition is suspected and genetic testing is not recommended in clinically-idiopathic SCA survivors.

OBJECTIVE

To investigate the diagnostic utility of broad, multi-phenotype genetic testing in clinically-idiopathic SCA survivors.

METHODS

Clinically-idiopathic SCA survivors underwent analysis of genes known to be associated with either cardiomyopathy or primary arrhythmia syndromes, following referral to a specialised genetic heart disease clinic in Sydney, Australia between 1997 and 2019. Comprehensive review of clinical records, investigations and re-appraisal of genetic data according to current variant classification criteria was performed.

RESULTS

In total, 22% (n = 8/36) of clinically-idiopathic SCA survivors (mean age 36.9 ± 16.9 years, 61% male) had a disease-causing variant identified on broad genetic testing. Of these, 7 (88%) variants resided in cardiomyopathy-associated genes (ACTN2, DES, DSP, MYBPC3, MYH7, PKP2) despite structurally normal hearts or sub-diagnostic structural changes at the time of arrest, so-called "concealed cardiomyopathy". Only one SCA survivor had a variant identified in a channelopathy associated gene (SCN5A).

CONCLUSION

Extended molecular analysis with multi-phenotype genetic testing can identify a "concealed cardiomyopathy", and increase the diagnosis rate for clinically-idiopathic SCA survivors.

Brugada Syndrome: Clinical Care Amidst Pathophysiological Uncertainty

Brugada syndrome (BrS) is a complex clinical entity with ongoing conjecture regarding its genetic basis, underlying pathophysiology, and clinical management. Within this paradigm of uncertainty, clinicians are faced with the challenge of caring for patients with this uncommon but potentially fatal condition. This article reviews the current understanding of BrS and highlights the "known unknowns" to reinforce the need for flexible clinical practice in parallel with ongoing scientific discovery.